Chapter 26 - The Reproductive System: Male

Describe the function of the bulbourethral glands. Include the components of seminal fluid and prostatic secretions.

(Cowper's glands) - marble-sized paired glands found at base of penis on either side of membranous urethra 1. Secrete a thick, alkaline mucus-like fluid that helps neutralize acidic urine remaining in urethra in response to sexual stimulation 2. Also lubricate glans penis during intercourse

Define male climacteric

(andropause) - period in which reproductive function begins to decline in men

Describe the function of the seminal vesicles. Include the components of seminal fluid and prostatic secretions.

- secretes seminal fluid; Composed of: a. Fructose - sugar that sperm utilize for ATP synthesis b. Prostaglandins - stimulate smooth muscle contraction in both gender's reproductive tracts and increase sperm viability c. Coagulating proteins and enzymes (both from prostate) - combine to form a temporary clot of semen in female reproductive tract - pH of seminal fluid is alkaline to neutralize acids in male urethra and female reproductive tract

Briefly describe the process of spermatogenesis and explain how men can make sperm throughout their remaining lifetime

1. Before puberty, spermatogonia divide only by mitosis to increase their numbers 2. After puberty, spermatogonia become fully functional stem cells a. Divide by mitosis allowing one daughter cell to remain a stem cell while other becomes a diploid primary spermatocyte 3. Continual replacement of stem cell allows sperm production throughout a male's life 4. Primary spermatocyte continues to become sperm - Spermatogenesis begins with a spermatogonium that has 46 chromosomes, and produces 4 spermatids that have 23 chromosomes each.

Explain the similarities in the male and female reproductive systems

1. Gonads (primary sex organs) are most important organs for both genders a. Male gonads: testes b. Female gonads: ovaries 2. Gonads secrete sex hormones, including testosterone and estrogen 3. Gonads produce gametes (sex cells) through process of meiosis a. Male gametes: sperm b. Female gametes: ova, or egg cells 4. Both genders have additional organs and structures called accessory reproductive organs that contribute to functioning of their respective systems

Describe the structure of a mature sperm

1. Head - contains nucleus and acrosome and very little cytoplasm 2. Midpiece - contains mitochondria that generate ATP to power flagellum 3. Tail - mostly composed of flagellum

Describe testosterone's effects on other body systems

1. Secondary sexual characteristics: growth of pubic, axillary, and facial hair as well as increased hair growth in specific regions of body, such as chest 2. Larynx enlarges and vocal cords thicken; results in a noticeable "Adam's apple" and deepening voice 3. Skin thickens and sebaceous glands increase secretion 4. Testosterone causes somatic effects, many of which are anabolic in nature a. Bone density increases as a greater amount of calcium salts are deposited; skeletal muscle mass also increases b. Erythrocyte production increases as testosterone increases erythropoietin secretion 5. Testosterone influences behavior; basis for male libido

Explain the effects of aging on reproductive function in males

1. Size and weight of testes may decrease 2. Number of sustentacular and interstitial cells may decline a. Secrete less inhibin and less testosterone 3. Reduced levels of testosterone are associated with: a. Gradual decrease in production of sperm cells b. Depressed mood and fatigue in some individuals c. Loss of muscle mass and a decrease in bone density 4. Prostate gland hypertrophy occurs a. Often compresses urethra, leading to difficult urination

Explain how the scrotum and spermatic cord work together to support sperm production through temperature regulation. Include the roles of the countercurrent heat exchanger, the cremaster muscle and the dartos muscle.

A. Scrotum -contains testes 1. A midline septum divides scrotum into two internal compartments, one per testis 2. Scrotum wall contains an outer layer of skin, superficial fascia, and a layer of smooth muscle called dartos muscle B. Spermatic cord - tube extending from scrotum; contains ductus deferens, blood and lymph vessels, and nerves; leads to pelvic cavity 1. Cremaster muscle - smooth muscle that controls height of testes C. Both scrotum and spermatic cord work together to support sperm production by regulating temperature 1. Normal core temperature (37 degrees C) is too warm for mass production of viable sperm cells a. Scrotum is generally 3 degrees C cooler D. Temperature regulation is managed by following mechanisms: 1. Countercurrent Heat Exchanger: blood vessels are arranged allowing for heat transfer as arteries and veins carry blood in opposite directions; reduces scrotum temperature 2. Scrotum temperature can be increased or decreased by altering distance from body by using cremaster muscle a. When cold, scrotum is drawn closer to body; when warm scrotum is relaxed and moves away from body 3. Surface area of scrotum adjusted by using dartos muscle a. Surface area is minimized in cold weather to decrease heat loss b. Surface area of scrotum is increased when too warm; allows for greater heat loss

Discuss the composition of semen and its role in sperm function

A. Semen - somewhat sticky whitish mixture of sperm (makes up about 5% of semen volume) and all fluids from testes, seminal vesicles, prostate, bulbourethral and urethral glands; B. Typical ejaculate (amount of semen expelled during one ejaculation) is between 2.5 and 5 ml in volume 1. Contains between 40-750 million sperm cells C. Coagulation occurs five minutes post-ejaculation1. Prevents semen from leaking out of female reproductive tract D. PSA and prostate anticoagulants break clot after 15-30 minutes 1. Sperm cells are gradually released from clot, activated, and begin their ascent up female reproductive tract E. Alkaline pH of semen helps to make sperm fully motile and to begin process of capacitation F. Prostaglandins stimulate contractions in female reproductive tract and possibly thin mucus 1. Allow sperm access further into female tract increasing probability of fertilization G. Antimicrobial chemicals from prostate kill some bacteria including Escherichia coli

Further explain the role of the sustentacular cells

A. Sustentacular cells (nurse cells, Sertoli cells) - surround spermatogenic cells to provide support B. Sustentacular cells, bound together by tight junctions, extend from basement membrane to seminiferous tubule lumen 1. Forms blood-testis barrier; prevents immune system cells in bloodstream from detecting newly formed antigens on newly formed, genetically unique sperm cells C. Sustentacular cells also perform following functions vital for normal spermatogenesis: 1. Provide structural support for stem cell development and secrete testicular fluid; helps transport sperm in seminiferous tubule 2. Provide nutrients for dividing cells and produce androgen-binding protein (ABP) and inhibin, which help regulate spermatogenesis 3. Phagocytize damaged spermatogenic cells and excess cytoplasm released from maturing spermatids

Explain the hormonal control of male reproduction

A. Testosterone - main hormone involved in regulation of spermatogenesis and male reproductive physiology B. Ultimately, testosterone stimulates spermatogenesis and development of male characteristics C. Hormones of Male Reproduction: See Table 26.3

Define capacitation

Process that enables sperm to penetrate and fertilize an immature female gamete

Define zygote

cell that divides to produce all of cells in a new individual

Describe the function of the prostate gland. Include the components of seminal fluid and prostatic secretions.

egg-sized gland found inferior to urinary bladder; surrounds urethra and ejaculatory ducts 1. During ejaculation, prostatic smooth muscle contracts; squeezes prostatic secretions into prostatic urethra via several ducts 2. Prostatic secretions - make up 20-30% of semen volume; milky fluid that contains: a. Citrate - another sugar that sperm can utilize for ATP synthesis b. Prostate specific antigen (PSA) and other enzymes - dissolve semenclot in female reproductive tract to allow sperm to proceed further into tract c. Antimicrobial chemicals - inhibit some bacterial growth to decrease risk of infection in female reproductive system 3. pH is alkaline to neutralize acids in urethra and female reproductive tract

Describe the roles of the epididymis and the penis

epidermis is filled with ductules and is site of sperm maturation and storage; penis delivers sperm into female reproductive tract

Describe the roles of each of the following cells: interstitial

found between seminiferous tubules; produce and secrete androgens, primarily testosterone, into surrounding interstitial fluid

Describe the roles of each of the following cells: myoid

muscle-like cells that surround seminiferous tubules; contract to push sperm and testicular fluid through tubules

Explain the functions of the testes

perform two important functions: 1. Sperm production 2. Secretion of androgen hormones, primarily testosterone

Define fertilization

process by which a sperm and egg cell fuse to form a new cell called a zygote

Define meiosis

process during which a cell divides to form daughter cells with half number of chromosomes

Define spermatogenesis

process in which male gametes, or sperm cells, develop; begins at puberty and continues for duration of lifespan

Define spermiogenesis and explain the process

process of sperm maturation; involves cellular shape and size changes Process: 1. Begins in testes as spermatids elongate and shed excess cytoplasm 2. An acrosome develops; covers nucleus and helps with fertilization of female gametes 3. Mitochondria increase in numbers and move to developing flagellum site4. Spermatids separate from sustentacular cells and are released into seminiferous tubule lumen5. Spermatids develop a head, midpiece, and tail as they mature into sperm cells

Trace the pathway of sperm from the seminiferous tubules to the external urethral orifice of the penis

seminiferous tubules, straight tubule, rete testis, efferent ductules, epididymus, ductus deferens, ampulla, ejaculatory duct, prostatic urethra, membranous urethra, spongy urethra, & penis

Describe the roles of each of the following cells: spermatogenic

sperm-forming cells

Define spermatogonia

stem cells that initiate spermatogenesis

Describe the roles of each of the following cells: sustentacular

support sperm production